1. Field of the Invention
The invention relates to an audio signal processing arrangement for deriving a center channel signal from a stereophonic signal that includes a left and a right channel signal.
The invention further relates to an audio visual reproduction system comprising a picture display device, a first loudspeaker for reproducing a left channel signal, a second loudspeaker for reproducing a right channel signal and a third loudspeaker for reproducing a center channel signal, the audio visual reproduction system comprising an audio signal processing arrangement of the type defined above.
2. Description of the Related Art
The use of a center channel signal in a stereophonic reproduction system has the effect that the position of the perceived virtual sound sources depends less on the position taken up by the listener with respect to the left and right loudspeakers. This is especially important in the case where the reproduction of stereophonic information is combined with a picture display device such as, for example, television with a stereophonic reproduction system. For, when a displayed audio visual program is followed, it is important that the position of the virtual sound sources be not perceived far from the position of the picture screen.
A circuit for deriving a center channel signal is known from U.S. Pat. No. 4,034,344.
In the circuit described in above Patent, there is determined by comparison whether the low-frequency region of the audio signal spectrum comprises correlating components. For this comparison, the low-frequency signal components in the left channel signal are multiplied by the low-frequency components in the right channel signal. The DC component of the result of the multiplication is compared with the sum of the DC components of the rectified channel signals. Depending on the result of the comparison, a larger or smaller part of the sum of low-frequency components of the left and right channel signals is used as a center channel signal. A drawback of prior-art circuit is the relatively small degree of accuracy with which the correlation is determined.